This invention relates to polyelectrolyte complexes, more particularly to thermoplastic polyelectrolyte complexes.
Polyelectrolyte complexes (PEC) are prepared by the reaction of a polyanion (PA) and polycation (PC) to form an ionically crosslinked polymer. Said PEC are usually the reaction product of a polyanion containing a plurality of strong acid groups such as sulfonic acid groups and the polycation having a plurality of strong base groups, i.e., quaternary ammonium groups. Such PEC are described in various references including, for example, U.S. Pat. Nos. 3,276,598; 3,546,142; 3,558,744 and 3,565,973 to Michaels. PEC have unique properties which make them especially suitable for use as battery separators, antithrombogenic plastics, inverse osmosis dialysis or ultra-filtration membranes, antistatic agents, dye acceptors and components in artificial leathers.
Unfortunately, difficulties in processing PEC into useful forms greatly restrict the wide-spread application of these complexes. Conventional PEC are not thermoplastic, i.e., they are not moldable or extrudable, so they must be handled as solutions. See Michaels, "Polyelectrolyte Complexes," Kirk Othmer Encyclopedia of Chemical Technology, 2nd Ed., Vol. 16, page 119, (1968). However, most conventional PEC are not soluble in water or organic solvents and must be dissolved in a ternary system of water, inorganic salt and a polar organic solvent such as dioxane or acetone. The proper proportions of water; salt and organic solvent in said ternary solvent systems must be experimentally determined for each PEC. The dissolved PEC must be recovered by the removal of the solvent or by adjusting the composition of the ternary solvent so that the PEC is no longer soluble therein. Generally, large amounts of water are added to the ternary solvent to precipitate the PEC. Recently, Merze, in U.S. Pat. No. 4,118,437, has developed organic soluble PEC. However, the use of such PEC still requires the use of solvents which must be removed to recover the PEC in the desired form. Because of these difficulties in working with solutions of conventional PEC, it would be desirable to have an easily handled PEC.
In addition, conventional PEC generally have poor mechanical properties, i.e., they are hard and brittle and must be plasticized or combined with other materials to provide mechanical strength. However, since PEC are not moldable or extrudable, combining the PEC with plastics and other fillers is difficult and generally yields poor results.
Accordingly, it would be desirable to have an easily processable, thermoplastic PEC which can be readily blended with plastics and fillers.